Life-span alterations in visually evoked potentials and inhibitory function.

Visually evoked potentials (VEPs) elicited by patterned and unpatterned flashes were recorded from 211 healthy males aged 4-90 years. A measure of similarity between the two kinds of VEPs was obtained by correlating the digital values comprising the two waveforms. Across the life-span, correlations followed a U-shaped curve; patterned and unpatterned flash VEPs were most alike for the youngest and oldest subjects. This age effect, localized to scalp areas overlying visual cortex, is compatible with a concept of reduced inhibitory functioning within the visual systems of the young and the old. At central scalp, patterned and unpatterned flash VEP waveforms were more effectively differentiated by the right hemisphere. This observation agrees that the right hemisphere specializes in analyses of spatial material.